error on VHDL program....please help me...=)

[energy_baz]

hi...

I need a help to fix this error....the error states

Line 25: Found 0 definitions for operator "-".

and this is my program code and I had highlight the error in pink color....thanks..

 

[FvM]

You have to observe VHDL syntax rules. To assign an integer quantity to an unsigned signal, it has to be converted to unsigned before. IEEE numeric_std library has the TO_UNSIGNED() function for this purpose. Consult a VHDL text book or the library definition.

 

[sachingorkhe]

You need to add unsigned library for using signed/unsigned numbers to be used in your code.
Also try to use '(' brackets to complete any expression bonding.

~Sachin

 

[alexan_e]

You need to add unsigned library for using signed/unsigned numbers to be used in your code.
Also try to use '(' brackets to complete any expression bonding.

~Sachin

The IEEE.NUMERIC_STD library already covers signed & unsigned.

Alex

 

[FvM]

"IEEE".STD_LOGIC_UNSIGNED is a non-standard Synopsys library, used by lazy VHDL programmers to save a few lines of code. It introduces a behaviour similar to Verilog, where bit vectors (std_logic_vector) are treated as unsigned numbers by default. It thwarts the clear VHDL type concept and causes confusion, if both signed and unsigned are used in a VHDL design.

The code has already more brackets than needed by the VHDL standard. But it's O.K. to use them in case of doubt about operator precendence, I think.